It is narrated from Tawoos (may Allah have mercy on him) that Umar bin Khattab (may Allah be pleased with him) asked: "I put under oath by Allah the one who has heard anything from the Prophet ﷺ regarding the fetus (unborn child in the womb)?" So Haml bin Malik bin Nabighah (may Allah be pleased with him) stood up and said: "I used to live between my two wives. One of them struck the other with a tent pole, and she miscarried a dead fetus. In this matter, the Messenger of Allah ﷺ ruled for a slave or a slave-girl." Then Umar (may Allah be pleased with him) said: "It was close that we would have given a verdict in this matter based on our own opinion."
Hadith Referenceمسند الإمام الشافعي / كتاب القتل والقصاص والديات والقسامة / 1651
Hadith Takhrijاخرجه أبو داود الديات، باب دية الجنين، رقم: 4572 - وابن ماجة، الديات، باب دية الجنين (2641)۔ والنسائي (4743) موصولا وصححه ابن حبان والحاكم: (3/ 575)۔